Geololgy Chapter 7, Interlude B - flashcards

Sedimentary Rocks

Quiz Friday 7.2

Exam on Friday 3/15***

Minerals, igneous, sedimentary, volcano

5,15,6,9,7

Rock Cycle

Sedimentary Rocks→ Lithified sediments, forms when rock debris transported by the agents of erosion solidify. Cools deep below the ground

Covers 75-80% of Earth’s surface

Only 5% of outer 15 km (very thin)

Extremely important for resources

Oil, natural gas, coal, sand, gravel, ores, salt, clay

Sedimentary Cycle:

Break down of rocks → weathering

Climate, topography, composition

Weathering → regolith (loose material that is the end product of weathering)

Movement/deposition of sediments → erosion

Water, wind, ice, gravity (over steeping)

Erosion → sediments

Source Area

The more chemically weathered rock is, the more likely it will undergo mechanical weathering

The smaller the rock = the more surface area = the more prone to weathering chemically.

Steps of Mechanical Weathering

Mechanical weathering → physical breakup of rock, dominant process in cool/dry climates, maintains mineral compositions

Chemical weathering → changing the chemical makeup of the rock

Mechanical exfoliation, pressure release

Ex: Exfoliation domes, e.g. Stone Mountain

Frost wedging

Ex:H2O volume increases 9%, 30,000 psi

1. Talus cone, Talus slope– frost wedging

1. Crystal growth

→ tafoni, honey-combed– areas with salt spray

1. Thermal expansion

→ Quartz expands 3x as much as feldspar

1. Abrasion

→ stones grinding together, gradually gets more flat or spherical

1. Biological

• Root wedging: roots work their way down into the cracks of the rocks, slowly pushing the rocks away from each other.

• Tree roots break up the rock’s mass, allowing water to come in

Chemical Weathering

• Dominant processes in warm/humid areas, alters mineral composition

• Regolith: end products of weathering that has not been transported

• Temperature and precipitation affect the depth of chemical weathering front, depending on the situation

1. Dissolution: as the rock is exposed to the elements, the rock will dissolve. The component parts are taken apart, and suspended by a water body.

• Ex: calcite, halite, anything that is a limestone

1. Oxidation: oxygen and a metal, producing rust

• Oxygen binding to iron

1. Hydrolysis: H2O breaks down and reacts with the crystalline structure of the other minerals and changes their composition; it is an acidifying agent

• Ex: change granite to kaolinite+quartz

• Quartz is the most resistant mineral to chemical weathering.

• Orthoclase and plagioclase weathers away quicker

Spheroidal Weathering

• Weathering attacks the corners and edges of a rock the quickest, and the faces the rock the slowest, ultimately creating a spherical shape

• Ex: Veta Vu

Weathering Produces Soils

• 0 Horizon- A2 Horizon: Topsoil

• B Horizon:

• Clay formation

• C Horizon

Sedimentary Rocks

• Lithified sediments

• Compaction, dewatering, cementation

• Water escapes under pressure, allowing ions to come into the groundwater level

• Strata

• Picture: Breccia that is oxidized

Sedimentary Environments

• Conglomerate → river deposit

• Sandstone → beach or desert

• Shale → Ocean, lake, swamp

• Terrestrial Environment

• Alluvial fan- Breccia

• Glacial- Till

• Sand dunes- Sand

• Marine Environment

• Reef system

• Submarine fan- Underwater land slides that happen on the continental slope → turbidite

**Sedimentary Rock Types

1. Clastic: broken bits of other rocks

• Sedimentary, igneous, etc..

• Rounded clasts: Conglomerate

• Angular clasts: sedimentary

• Shale: smaller compaction

• Siltstone: thicker compaction

• New Oreleans: the Delta compacts below the city, creating a decrease in elevation.

1. Organic: remains of plants

• Ex: coal, oil shale

1. Chemical: evaporites & cherts nodules

• Gypsum, silica (chert nodule)

• River that runs into the dead sea: Jordan River

• Runs into a desert and evaporates

1. Carbonates (biochemical): limestones, coquina, ooids, chalk

• Warm and most likely shallow marine environments

• We use limestone to create cement

• Ex: travertine, oolitic, phosphorus, micrite,

• Limestone fizzed under hydrochloric acid

• Ooids: forms in shallow areas

• Small and round

• Chalk: silica, calcium carbonate

Sedimentary Rock Features

• Sorting:

• Alluvial fan: Very poorly sorted (larger angular pieces)

• Maturity: how long a rock has been exposed to weathering

• Alluvial Fan: Immature

• Beach: Mature

• Cross bedding: Movement by water or wind

• Ripple Marks symmetrical/asymmetrical: tide pools

• Vertical ripple marks: uplift of seafloor

• Mud cracks

• Graded bedding: particles grade up to finer particles.

• Fast flowing water: small sediments

• Slow slowing water: larger sediments

• Color red: (Iron oxide makes this color

• Floodplain, alluvial fan

• Black: (Carbon and pyrite makes this color)

• Swamps

• Alluvial fan: forms breccia, feldspars, clay

• Delta: when a stream carries a sediment into a larger body of water
  - creates conglomerate stones

- creates mudstones off the shore

- bottomset: mud

- Foreset beds:

- Top set beds:

• Lake Bonneville: water levels decreased over time, but delta deposits still stayed

Rock facies changes in sea level, transgression, regression

• Limestone: off shore

• Shale: intermediate

• Sand: beach/proper

• As sea level rises, sediments move towards land

• As sea level falls, sediments move towards the ocean

• Transgression: Sea level is rising over the land

• Regression: Sea level is falling off the land and into the ocean

• Sea level rise: Interglacial rising

Questions:

How do Alluvial fans work?

Question: How do we preserve sundunes, sandstone mountains

• As ground water comes up from below, it saturates the bottom on the dunes, but leaves the top of the dunes dry, allowing sand dunes to grow more

Exam: 15 FIB, 20 MC

• Draw and label rock cycle

• Distinguish volcano types

• Know Geological Features

• Ex: Mtns, Lakes, Volcanos

• Ring of Fire: Pacific Ocean is surrounded by volcanoes

→ Ring of subduction: Oc-Con, Oc-Con ,Oc-Oc

• Study Quizzes

• igneous rock forms around convergent conbaries

• How hot does it take for Igneous rocks to melt

• Now sediment sizes (sand, mud, gravel)

• Mechanical: physically breaks apart / Chemical: changing the mineral composition

• Characteristics that define a mineral

• Silicates, non-silicates, halites, etc, etc